Semiconductor light sources, such as light emitting diodes (LEDs), high power LEDs, organic LEDs (OLEDs) and laser diodes are known to be energy efficient and small light sources that have a small/low etendue (i.e. the product of emitting area with solid angle in which the light is emitted). This implies that these semiconductor light sources emit light from a relatively small area into a limited angular range.
Such semiconductor light sources may therefore be beneficial for applications where a bright light source is needed. Typical example applications include projection systems, automotive lighting, camera flashlights, and spot lights. For these examples, improved miniaturization is often desirable. However, merely reducing the size of a semiconductor light source reduces the generated light flux.
It is known to obtain increased luminance from a semiconductor light source by means of a mix box with a small aperture (i.e. light output section) from which the light can escape. FIGS. 1A and 1B illustrate a known LED-based light source 10 employing this concept, wherein light generated by a LED 12 (on a die substrate 14) is recycled/reflected in a mix box (formed from material 16 having high reflectivity) until it escapes via a small aperture 18. By the aperture 18 being “small” it is simply meant as being smaller than the LED 12 such that the aperture area AA (i.e. width WA×LA) is less than the LED area ALED (i.e. width WLED×LLED) of the LED 12.
It is also known to form the aperture 18 from a luminous ceramic material or other phosphorescent material.